MR coronary angiography: 2001 update.

Cardiovascular magnetic resonance (CMR) has developed multiple techniques that have made it possible to overcome the substantial difficulties in imaging coronary arteries. Tortuous small coronary arteries are imaged in 3D-volume data sets. Cardiac motion is reduced by diastolic gating with ultra-fast sequences. Respiration is suppressed by breath-holding or respiratory gating. Signal-to-noise can be increased with contrast agents. In clinical trials CMR has been successfully used to assess coronary artery stenoses, coronary artery bypass grafts, and anomalous coronary arteries. Recent developments in steady state imaging, volume selective imaging with tracking, parallel imaging techniques, vessel wall imaging, and intravascular contrast agents may soon enable CMR of the coronary arteries to become an effective and widespread clinical tool.

Magnetic resonance of coronary arteries.

Magnetic resonance coronary angiography (MRCA) is developing rapidly as a non-invasive method for assessing coronary artery anatomy and function. This article reviews the issues involved in MRCA and the methods used to overcome them. The current clinical applications for MRCA are then summarised with reference to published clinical studies.

Coronary MRA--a clinical experience in Europe.

This review concentrates on contributions from European centers to magnetic resonance (MR) imaging of the coronary arteries. Coronary MR angiography has developed rapidly over the last 10 years, and there has been considerable interaction between Europe and the United States in the technical and clinical developments during this time. The major problems of coronary imaging have been gradually overcome with the combined use of respiratory and cardiac gating, as well as three-dimensional imaging. The ultrafast techniques such as spiral and echoplanar methods are likely to play a larger role in the future, and flow measurements are becoming possible. The next millennium should see the adoption of these techniques into routine clinical practice to allow the safe non-invasive diagnosis of coronary artery disease.J. Magn. Reson. Imaging 1999;10:721-727.

Anomalous coronary arteries: anatomic and functional assessment by coronary and perfusion cardiovascular magnetic resonance in three sisters.

Combined coronary and perfusion cardiovascular magnetic resonance was performed in three sisters with angina and suspected anomalous coronary arteries. Two sisters had anomalous coronary arteries passing between the aorta and right ventricular outflow tract and had abnormal myocardial perfusion. One sister had normal anatomy and perfusion. The combined approach identified the anatomy and functional significance of suspected anomalous coronary arteries.

Phase ordering with automatic window selection (PAWS): a novel motion-resistant technique for 3D coronary imaging.

Navigator acceptance imaging methods are hindered by the loss in scan efficiency which results from the changes in the breathing pattern of a subject over time. The diminishing variance algorithm (DVA), which does not use a predefined acceptance window, is less influenced by such changes. The use of phase ordering and weighting techniques has been shown to significantly improve image quality over nonordered window methods. However, the use of an acceptance window is inherent in all these techniques as a decision to accept or reject data must still be made. A technique is presented which is resistant to changes in breathing while allowing the use of phase ordering to provide effective motion artifact reduction in optimal time. The basic principle is described and illustrated for this automatic window-selection technique with in vitro results to demonstrate the feasibility of this method. Results of an in vivo study are also presented which demonstrate significant improvement in image quality over the DVA (p < 0.01) and hybrid-ordered phase encoding methods (p < 0.05).

Evaluation of free-breathing three-dimensional magnetic resonance coronary angiography with hybrid ordered phase encoding (HOPE) for the detection of proximal coronary artery stenosis.

We evaluated free-breathing, prospective navigator-gated, three-dimensional (3D) magnetic resonance coronary angiography (MRCA) with hybrid ordered phase-encoding (HOPE), in the detection of proximal coronary artery stenosis. The coronary arteries were imaged in 46 patients undergoing cardiac catheterization. The mean scan time was 48 minutes. The mean arterial length (mm) visualized was left main stem (LMS) 11.7 (SD 4.5), left anterior descending (LAD) 30.1 (SD 11.1), circumflex (LCx) 15.5 (SD 8.6), and right (RCA) 56.2 (SD 20.8). Twenty-three patients had coronary artery disease with 47 significant stenoses on cardiac catheterization. All LMS were normal on both catheterization and MRCA. MRCA sensitivity was highest for the LAD (89% CI 65%-99%) and RCA (76% CI 50%-93%), but lower for the LCx (50% CI 21%-79%). Specificity ranged from 72%-100%. Improvements in image quality, length of vessel seen, and specific imaging of the LCx are required for MRCA to become an alternative to cardiac catheterization.

Improved cine cardiovascular magnetic resonance using Clariscan (NC100150 injection).

We evaluated the use of Clariscan 0.75, 2, and 5 mg Fe/kg body weight in six patients to determine optimal dosing for short repetition time cine imaging. Breathhold cine images were acquired in the vertical and horizontal long axes and the short axis. Blood-pool signal-to-noise ratio increased significantly in all planes (p < 0.01) but was least marked in the short axis. Myocardial signal-to-noise ratio increased by a lesser amount (p < 0.05). Myocardial to blood-pool signal-difference-to-noise ratio improved significantly in the long axes (p < 0.05) and was greatest at 2 mg Fe/kg body weight, but changes in the short axis were minor. With the 5-mg Fe/kg body weight dose, the response was reduced or reversed due to T2* effects. Visual assessment improved in all planes (p < 0.05) and was optimal at 2 mg Fe/kg body weight. In conclusion, Clariscan improves short repetition time cardiac breathhold cine imaging, particularly in the long axis planes, with an optimal dose of 2 mg Fe/kg body weight.

Cardiovascular T2-star (T2*) magnetic resonance for the early diagnosis of myocardial iron overload.

AIMS: To develop and validate a non-invasive method for measuring myocardial iron in order to allow diagnosis and treatment before overt cardiomyopathy and failure develops. METHODS AND RESULTS: We have developed a new magnetic resonance T2-star (T2*) technique for the measurement of tissue iron, with validation to chemical estimation of iron in patients undergoing liver biopsy. To assess the clinical value of this technique, we subsequently correlated myocardial iron measured by this T2* technique with ventricular function in 106 patients with thalassaemia major. There was a significant, curvilinear, inverse correlation between iron concentration by biopsy and liver T2* (r=0.93, P<0.0001). Inter-study cardiac reproducibility was 5.0%. As myocardial iron increased, there was a progressive decline in ejection fraction (r=0.61, P<0.001). All patients with ventricular dysfunction had a myocardial T2* of <20 ms. There was no significant correlation between myocardial T2* and the conventional parameters of iron status, serum ferritin and liver iron. Multivariate analysis of clinical parameters to predict the requirement for cardiac medication identified myocardial T2* as the most significant variable (odds ratio 0.79, P<0.002). CONCLUSIONS: Myocardial iron deposition can be reproducibly quantified using myocardial T2* and this is the most significant variable for predicting the need for ventricular dysfunction treatment. Myocardial iron content cannot be predicted from serum ferritin or liver iron, and conventional assessments of cardiac function can only detect those with advanced disease. Early intensification of iron chelation therapy, guided by this technique, should reduce mortality from this reversible cardiomyopathy.